Hi all.
Some help please.
For some equipment (CNC machine, now in hobby use) I have a small burned out 6VA PCB transformer.
Long story short, I cannot find it, but I found someone willing to custom made one, so I need the exact specs.
Which are all clear to me, except the polarity. (and yes, in this case polarity is important)
The vendor told me it is usual for him, and without instructions he will simply, wind all coils clockwise from low pin number to high pin number.
I need some help interpreting what I measured please.
My measurement setup is such:
- On a friends different still working machine, not allowed to disassemble, I measured hot.
- Scope behind an isolation transformer
- Scope in AC trigger mode. That means it will always trigger on the same point in the 50Hz phase
- First I put GND on pin 1 (low pin) and probe on pin 5 (high pin) for the 400V high side (picture 1 left)
- Next I put GND on pin 6 (low pin) and probe on pin 7 (high pin) for the 1st 18V (picture 1 right)
- In this machine I can not reach pins 8,9,10 to measure the other coils.
(Note: The Rigol *overwrote* my USB stick images on the second measure setup, but lucky I also made a (tiny) hand sketch)
Please confirm, but I think this shows the 18V is wound in the *opposite* direction from 400
And thus opposite to what vendor tells me is usual.
Next I also measured the 3 secondary coils on the broken & burned transformer (primary coil being busted)
Using the same 6-7 18V coil as comparative baseline
- Scope behind an isolation transformer
- Scope in AC trigger mode. However, different house, different location, different phase
- I put 12V AC on pin 6 and 7 (with a 220R current limit resistor)
- First I put GND on pin 6 (low pin) and probe on pin 7 (high pin) (picture 2) to reset baseline
- Next I put GND on pin 7 (now low pin) and probe on pin 8 (high pin) (picture 3)
- Next I put GND on pin 9 (low pin) and probe on pin 10(high pin) (picture 4)
Please confirm, but I think this shows the 16V is also in the opposite direction from the 18V
And thus the 16V is normal direction related to 400V
And the overall conclusion is that *only* both 18V coils are opposite, and they are indeed opposite to convention.
Please also tell me, following convention, where would I put the dots in the attached transformer pinout schematic
Many thanks
Maurits